1. Field of the Invention
The present invention relates to a display device, and more specifically, it relates to a technique for reducing power consumption and simplifying a circuit configuration.
2. Related Background Art
Monochrome display devices were often provided in conventional mobile instruments such as mobile phones. Recently, with increase of opportunities such as connections to an Internet using the mobile instruments, the mobile instruments having color display devices has increased.
Since power consumption in the color display device is larger than that in the monochrome display device, the color display device has a problem that an interval of battery charging of the mobile instrument is short. Furthermore, since a circuit is also complicated, miniaturization is difficult, which leads to increase in cost. In particular, it is desirable to integrally form a driving circuit on a pixel array substrate in order to reduce size of the mobile instruments. In case of the color display device, however, not only the structure of the driving circuit is complicated, but a capacity of a memory storing therein pixel data is also increased. Therefore, it is technically difficult to integrally form the driving circuit on the pixel array substrate.
Furthermore, in the prior art, since display areas are all rewritten at fixed intervals, a frequency of a pixel clock has to be accelerated as a display resolution is increased.
As a countermeasure for solving such a problem, for example, Japanese Patent Application Laid-open No. 227608/2000 discloses a technique for rewriting the display content by selecting and scanning only horizontal pixel lines in which the display content is changed.
In such control in accordance with each horizontal pixel line, however, the low-consumption power is not necessarily attained as compared with control at the time of usual driving.